1. Field of the invention
The present invention relates to the preparation and uses of alpha-glycosyl rutin.
2. Description of the prior art Rutin, whose chemical structure is given below, has been known as a yellow pigment and vitamin P with physiological activities such as stabilization of blood vessels, prevention of hemorrhage and regulation of blood pressure, and used from ancient times in foodstuffs, pharmaceuticals and cosmetics. ##STR1##
It is known that vitamin P takes part in some of the physiological activities of vitamin C in vivo; for example, in the hydroxylation of proline and lysine which are necessary to synthesize collagen as the main element of living connective tissues; the oxidation-reduction reaction of cytochrome C wherein Fe+++ is reduced into Fe++; and in the immunopotentiation via the increase of leukocyte. These are because vitamin P plays a significant role in the maintenance and promotion of health in living bodies.
Nowadays the use of rutin is not limited to agents which enrich vitamin P as a nutritive element, but is extending in various applications. More particularly, because of its chemical structure and physiological activities, rutin is useful as a yellow coloring agent and antioxidant alone or in combination with one or more vitamins, for example, in foods, beverages and pharmaceuticals for susceptive diseases such as preventive and remedy for circulatory diseases, as well as a yellow coloring agent and uv-absorbent in cosmetics such as skin-refining and skin-whitening agents.
Rutin is, however, hardly soluble in water (only about lg in 8 liters of water or about 0.01 w/v % at ambient temperature). This renders its practical use very difficult.
To improve this low water-solubility, some methods have been attempted. For example, Japanese Patent Publication No.1,677/50 disclose a method wherein aliphatic compounds with amino groups are added to rutin for its increased water-solubility; Japanese Patent Publication No.2,724/51, another method wherein monohalogeno acetic acids are allowed to act on rutin to convert it into sodium monohalogeno acetates having an increased water-solubility; and Japanese Patent Publication No.1,285/54, one another method wherein "Rongalit", a commercialized sodium hydroxymethane, is allowed to act on rutin to convert it into sulfite compounds having an increased water-solubility.
These methods have, however, the drawback that the use of amino compounds, monohalogeno acetic acids and sulfite compounds may result in an undesirable physiological activity and/or toxicity in final products, as well as rendering their purification very difficult.
We proposed a much safer solubilization method in Japanese Patent Publication No.32,073/79, wherein a biosynthesis by saccharide-transferring enzyme is utilized to transfer equimolar or more glucose residues from a partial starch hydrolysate to rutin to form alpha-glycosyl rutin having an improved water-solubility.
The alpha-glycosyl rutin obtained by the method would have an extensive use because it exhibits the same physiological activities as does intact rutin, and is free from toxicity, highly soluble in water, and therefore easily handleable. Thus, the realization of alpha-glycosyl rutin has been in strong expectation.
Since alpha-glycosyl rutin has many advantages as described above, its commercialization has been in great demand.
However, the initial concentration for rutin, attainable by conventional methods, is about 0.1 w/v % at most, and this extremely increases and wastes water and energy cost for the preparation and purification of alpha-glycosyl rutin. This is one of the major causes which have hindered the commercialization of alpha-glycosyl rutin.